1. Field of the Invention
The present invention relates to display device fabrication. More particularly, the present invention relates to the technology and fabrication of flat panel displays, e.g., field emission displays.
2. Related Art
Advancements in electronics and computer display technologies have created new categories of display devices as well as enabling improvements upon existing display technologies. New categories of display devices include FPDs, (flat panel displays), e.g., TFTs (thin film technology), LCDs (liquid crystal display), AMLCDs (active matrix liquid crystal display), and the like. Improvements upon existing display technologies such as CRTs (cathode ray tube) include greater resolution, a more diminutive dot pitch, ever increasing display screen size, and the number of recognizable colors, which has increased from monochrome (two) color to 24-bit (over 16 million) colors and higher.
However, of the display technologies mentioned above, including LCDs, not one is without certain drawbacks. For example, neither LCDs or AMLCDs can provide adequate viewing when viewed from an off-center angle, and they require backlighting which requires yet more power. TFTs are subject to immense quality control difficulties associated with each pixel's switching element, produced using integrated circuit techniques. Further, most FPDs cost substantially more than a CRT of an equivalent size. In fact, none of the FPDs or CRTs have been able to meet all of the needs for improving power consumption, increasing brightness efficiency, increased video response, improved viewing angles, cooler operating temperatures, providing full color range, scalability, ruggedness, and packaging.
In an attempt to provide a display device which responds to and overcomes the above list of needs, another class of display devices which utilize flat panel display technology has been developed. This new class of FPD (flat panel display) is called a FED (field emission display), also commonly called TCRT (thin cathode ray tube). The TCRT display is, as the name implies, a thin cathode ray tube. Accordingly, the TCRT has, on the average, a thickness of +/−8 millimeters, whereas the thickness of a conventional CRT is usually over 100 millimeters, dependent upon the size of the display.
The TCRT display has numerous other advantages over the conventional CRT, including, but not limited to, greater power efficiency, reduced operating temperature which equates to longer life for the display, reduced weight and foot print, faster response time to fast-moving graphic images, e.g., streaming video, and many others.
Even with the above mentioned improvements, the TCRT is not without certain shortcomings. For example, fabricating a TCRT requires that the back cathode side and front anode side (also called the faceplate) portions of the TCRT display be sealed together under a vacuum, which forms the tube, through which the graphic images are presented. During the application of the vacuum concurrent with the sealing process, the vacuum can result in forces as high as high fourteen and one-half pounds per square inch bearing down on the two portions being sealed. To prevent the collapse of either of the sides, cathode or anode, support structures or walls disposed interposed between the two sides are needed to prevent such an occurrence. Because of the thinness of the TCRT display being fabricated, the support structures must be strong enough to support the cathode side and anode side during the vacuum and sealing process while being thin enough so as to not adversely deflect the electron beams. Further, the support structures must be relatively easy to manufacture and cost effective, or risk having an overly expensive display product price, effectively reducing possible market share.
In one example to attempt to provide a support structure for the back cathode side and/or the front faceplate, materials having a predominantly polymer base, e.g., polyimides or polyamides were implemented. Unfortunately, polymers such as polyimides and polyamides are prone to excessive gas emissions during tube operation, such that even after outgassing, they are well known in the art to continue to generate gas within the display tube upon electron bombardment during display operation. This continual generation of gas during display operation causes a reduction of display performance and also reduces the approximated lifespan of the display device. Additionally, the polymers, (polyimides and polyamides) are very expensive, both in raw materials and in the processing costs related to the construction of the wall supports. Further, these materials have a low reflective index, which reduces the overall performance of the display, and they exhibit poor electrical conductivity.
Additionally, in many of the above mentioned attempts to provide a support structure, a photoresist is added, then exposed to the pattern of the wall support, and developed. Accordingly, a step of sandblasting, also called etching, is utilized to remove all areas of materials not covered by a photoresist. Unfortunately, current sandblasting techniques are not without drawbacks, e.g., the residue of the sandblasting is difficult to contain, it is very difficult to stop erosion at the material/substrate interface without inadvertent sandblasting of the substrate, it is slow and therefore costly, and the precision of the sandblasting is predicated upon the grit size of the sand, which is commonly around ten microns.
Thus a need exists for a support structure that provides a reduction in emitted outgasses during display operation. Furthermore, it is desirable to provide a support structure that has increased reflective properties so as to provide greater luminous efficiency. It is also desirable to provide a support structure that is less costly to manufacture. It is further desired to provide a support structure that can be etched without damaging the substrate upon which it is disposed, and it is further desired to provide a method of etching that is clean, inexpensive, and highly accurate.